1. Field of the Invention
This invention relates to a sheet feed apparatus, method and computer readable medium and more particularly to a sheet feed apparatus, method and computer readable medium which is capable of performing sheet feed operations in an efficient manner to meet the requirements for quickly reading document sheets which are, in particular, printed on both sides (e.g., also referred to as xe2x80x9cdouble-sided printedxe2x80x9d).
2. Discussion of Background
Automatic sheet feed apparatuses are convenient, in particular, when you deal with a large number of sheets and therefore they are widely used for copying machines, facsimile machines, and so on. In one type of such automatic sheet feed apparatus, a sheet is transferred line by line relative to a fixed reading position and is automatically turned when both sides of the sheet are needed to be read. While turning one sheet, an automatic sheet feed apparatus can insert a succeeding sheet. That is, a closed sheet path built in such a sheet feed apparatus brings possibilities of multi-sheet handling so as to improve the sheet feed efficiency.
In recent years, there have been various techniques introduced for handling double-sided printed documents. One example is Japanese Laid-Open Patent Publication No. JPAP07-109060 (1995) which describes an automatic sheet feed apparatus having two paths each for ejecting a sheet after a reading operation and another two paths each for reversing a sheet so as to allow a double-sided reading operation in a relatively fast manner and also to collate a page order. However, this technique results in a complex apparatus with increased manufacturing costs.
Accordingly, an object of the present invention is to provide a novel automatic sheet feeding apparatus, method and computer readable medium which is capable of efficiently performing a sheet feeding operation for the requirements of double-sided reading operations.
To achieve the above and other objects, the present invention provides a novel automatic sheet feeding apparatus, method and computer readable medium which includes a sheet table, a sheet transfer mechanism, and a controller. The sheet table holds a sheet set including at least one sheet. The sheet transfer mechanism performs first, second, and third transfer operations, in a sequential manner. In the first transfer operation, a sheet is separated one by one from the sheet set placed on the sheet table and is transferred via a first connecting path to the reading position to receive a front-face sheet feeding operation. In the second transfer operation, the sheet is transferred via the first connecting path to the reading position to receive a rear-face sheet feeding operation. In the third transfer operation, the sheet is ejected. The sheet is reversed relative to a top and bottom orientation after passing by the reading position in each of the first and second transfer operations. The controller controls the sheet transfer mechanism to perform the first transfer operation relative to a succeeding sheet at one of a time before the third transfer operation is performed relative to a preceding sheet when the sheet has a shorter length than a predetermined value in a direction parallel to a transfer direction and a time after a preceding sheet passes by the reading position during the third transfer operation relative to the preceding sheet when the sheet has a longer length than a predetermined value in a direction parallel to the transfer direction.
The sheet transfer mechanism may include a first path member, a switchback member, and a second path member. The first path member provides a switchback path. The first path member is positioned under the sheet table and is connected to the reading position via a second connecting path to receive the sheet after one of the front-face and rear-face sheet feeding operations. The second connecting path includes a sheet eject portion for ejecting the sheet under control of the controller. The switchback member is mounted on the first path member. The switchback member forwards, holds, and reverses the sheet under control of the controller. The second path member is positioned under the sheet table and provides a reverse path through which the sheet passes and in which the sheet is held under control of the controller. The second path member is connected to the first path member at one end thereof to receive the sheet moved in a reversed direction from the first path member. The second path member is also connected to the first connecting path at the other end thereof to transfer the sheet to the reading position.
The sheet transfer mechanism may further includes a switchback member moving mechanism, mounted on the first path member, for moving the switchback member to free the sheet in the first path member. The controller controls the sheet transfer mechanism to perform the first transfer operation relative to a succeeding sheet before the third transfer operation is performed relative to a preceding sheet when the sheet has a longer length than a predetermined value in a direction parallel to the transfer direction. Further, the controller controls the switchback member moving mechanism to move the switchback member to free the preceding sheet during the third transfer operation so that the succeeding sheet of the first transfer operation is allowed to enter into the first path member in contact with the preceding sheet and then controls the switchback member moving mechanism to return the switchback member so as to reverse the preceding sheet and to send forward the succeeding sheet simultaneously.
The sheet feed apparatus may further includes a sheet eject tray, mounted under the first path member, for receiving the sheet ejected from the sheet eject portion of the second connecting path included in the transfer mechanism. The switchback member may include a drive roller rotatable in forward and reverse directions and a driven roller. The switchback member may include a drive roller rotatable in forward and reverse directions and a driven roller movable by the switchback member moving mechanism. The drive roller may be mounted under the driven roller on the first path member. The sheet transfer mechanism may further include a first detecting mechanism, mounted before the sheet eject portion on the second connecting path, for detecting a trailing edge of the sheet. The controller controls the sheet transfer mechanism to perform the first transfer operation relative to a succeeding sheet when the first detecting mechanism detects the trailing edge of a preceding sheet during one of the second transfer operation when the preceding sheet has a shorter length than the predetermined value in a direction parallel to the transfer direction and the third transfer operation when the preceding sheet has a longer length than the predetermined value in a direction parallel to the transfer direction. The sheet transfer mechanism may further include a sheet flow switch mechanism, mounted at a position downstream of the second connecting path, for switching under control of the controller between a first sheet flow in which the sheet is transferred through the second connecting path to the sheet eject tray, a second sheet flow in which the sheet is transferred through the second connecting path to the first path member, and a third sheet flow in which the sheet is transferred from the first path member to the second path member. The sheet transfer mechanism may further include a sheet feed mechanism, mounted upstream of the first connecting path, for separating the sheet from the sheet set placed on the sheet table and transfers to the reading position during the first sheet transfer operation and a third detecting mechanism, mounted downstream from the sheet feed mechanism and upstream from a point at which the second path member is connected to the as first connecting path, for detecting a sheet separated from the sheet set. The controller controls the sheet feed mechanism to perform the first sheet transfer operation after the preceding sheet passes by the reading position and to stop the first sheet transfer operation when detecting mechanism detects the succeeding sheet.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.